How Zika Virus Works

The female mosquito, who has to suck lots of blood in order to lay her eggs, spits the Zika virus into each her new snacks when she bites them.

Universal History Archive/UIG via Getty images

Zika is a mosquito-borne arbovirus (short for arthropod-borne virus) of the genus Flavivirus, family Flaviviridae — the same genus as yellow fever, dengue fever and West Nile virus [source: CDC]. It comes in two main flavors, or lineages — African and Asian, each with multiple strains. The Americas play host to the Asian lineage. Zika can infect a number of animals, such as elephants, lions, rodents and zebras, but humans and nonhuman primates seem to be its main reservoirs [source: Rogers].

Like many of its Flaviviral cousins, Zika's mosquitos of choice come from the Aedes genus, particularly the aegypti species native to Africa. In the U.S., these skeeters can be found in the Gulf Coast states, Georgia and South Carolina, the southern half of Arizona, and peppered across California and New Mexico. The virus likely makes a second home in aegypti's Asian counterpart, Ae.albopictus, which has American digs as far north as New Jersey and as far west as west Texas, with ranges extending into the southern third of Arizona and bits of California and New Mexico [sources: CDC, McNeil et al., Rogers]. Other aedine mosquitoescan carry the disease, too. For example, some believe that the 2013 French Polynesian Zika outbreak spread through the proboscises of Ae. polynesiensis [source: Rogers].

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Mosquito-borne Zika begins its cycle when a female, which requires blood to lay eggs, pokes a meal source and sucks in the virus along with her plasma Slurpee. Zika travels in the blood to the female's gut, later to return via her circulatory system to her saliva. Her spit's anti-clotting properties come in handy when she squirts it — and the virus — into a later meal [source: McNeil et al.].

In the tradition that that did so much to boost tourism on the Ebola River, Zika was named for the Ugandan forest in which it was isolated in 1947, first in a rhesus monkey and later in mosquitos. Zika antibodies were first found in humans in the early 1950s [sources: McNeil et al., Rogers]. Unfortunately, naming convention is not all Zika shares in common with Ebola. Like that hemorrhagic fever, Zika might "hide" and replicate in areas of the body — such as the brain, eyes, placenta and testes — that block immune response [source: Steenhuysen].

Once confined to Africa and Asia, in 2007 Zika began moving across the Pacific. By early 2015, it had already knocked around Brazil for at least a year. Although the outbreak there began in May 2014, cases had already shown up in Natal, capital of the state of Rio Grande do Norte, earlier that same year. This timing roughly lined up with the 2014 World Cup, which was partly held in Natal, although numerous other proposed sources are equally possible [sources: McNeil et al., Wade].

Now in a country with conditions ripe for mosquito population explosion, situated in a hemisphere with virtually no immunity, Zika spread quickly in 2015. And that's when the trouble really began.

Symptoms and Treatment

Only about 1 in 5 people infected with Zika virus develop symptoms. These generally include fever, rash, joint pain and/or red eyes (conjunctivitis) lasting a few days to one week. Headaches or muscle pain can also occur. Often these are so mild as to go unnoticed, but in rare cases, they can require hospitalization. Zika is only rarely deadly. Its incubation period remains unknown, but current estimates peg it at a few days to a week. No specific medicines exist — just treat the symptoms with rest and fluids, and use acetaminophen (not aspirin or other non-steroidal anti-inflammatory drugs [NSAIDs]) for fever and pain [sources: CDC, Rogers, McNeil et al.].